[TenTec] OMNI VI Transmit IMD

John Rippey w3uls@3n.net
Sat, 13 Apr 2002 12:35:23 -0400


	Something made me look up the January 1993 QST review of the OMNI VI and 
check its transmit IMD stats. The reviewer, Rus Healy, says (p. 67), "As 
Fig 1 shows, the transmitter's third-order IMD products are down almost 40 
dB, which is excellent for a rig with 13.8-V final-amplifier transistors."

	The QST review (11/00) of the FT-1000MP Mark-V says only, "The original 
'MP did pretty well in the IMD department, with worst-case third-order 
products down about 27 dB and fifth order products down about 43 dB (this 
was on 24.95 MHz)." With regard to the Mark-V, the reviewer, Rick 
Lindquist, focuses on the Mark-V's built-in Class A amplifier for its clean 
output. There is no mention of Class A-B results but, according to the 
graph accompanying the review, in Class A-B (i.e., normal) operation, the 
Mark-V's third-order products are 27 dB down and fifth order are 48 dB down 
(21.250 MHz), virtually identical to the earlier 'MP's results.

	Yaesu's final amplifiers in both the 'MP and the Mark-V have yielded 13dB 
worse IMD performance (albeit at 200 watts) compared to the OMNI VI's final 
amplifier, and by so doing they have met a (new to me) "doing pretty well" 
standard for third-order IMD products enunciated in the Mark-V review, 
which I take it lies somewhere between "excellent" on the one hand and 
"godawful" on the other.

	Note also ARRL is reporting in the May QST that the worst-case third-order 
transmit IMD number for the IC-746PRO is 25 dB down. I don't know if this 
means the IC-746PRO also has cleared the "doing pretty well" criterion.

	
73,
John, W3ULS